A stepwise retreat: how immune cells catchpathogens

To protect us from disease our immune system employs macrophages, cells that roam our body in search of disease-causing bacteria. With the help of long tentacle-like protrusions, macrophages can catch suspicious particles, pull them towards their cell bodies, internalise and destroy them. Using a special microscopy technique, researchers from the European Molecular Biology Laboratory (EMBL) now for the first time tracked the dynamic behaviour of these tentacles in three dimensions. In the current online issue of PNAS they describe a molecular mechanism that likely underlies the tentacle movement and that could influence the design of new nanotechnologies.

The long cell protrusions that macrophages use as tentacles to go fishing for pathogens are called filopodia. The internal scaffolds of these filopodia are long, dynamic filaments consisting of rows of proteins called actin. The filaments constantly grow and shrink by adding or removing individual actin building blocks. But the dynamic properties of the filopodia and the mechanical forces that they can apply are not fully understood. Using a special microscopy technique a team of researchers from the groups of Ernst Stelzer and Gareth Griffiths at EMBL could for the first time observe the tentacle dynamics in three dimensions and measure their properties to unprecedented detail.

?The filopodia stretch out from the cell surface and upon contact with a suspicious particle they attach to it and immediately retract to pull the particle towards the cell body,? says Holger Kress who carried out the research at EMBL and is now working at Yale University. ?We expected the tentacles to move in a continuous, smooth process, but surprisingly we observed discrete steps of filopodia retraction?

Highly precise measurements allowed the scientists for the first time to determine the speed and the force of the retraction and revealed that each individual retraction step is 36 nanometres long. These parameters match the properties of a class of proteins called myosins suggesting them as the driving force of filopodia retraction. Myosins are motor proteins, proteins that move along actin filaments and transport cargo. Transporting the filopodia?s internal scaffold myosins help bringing about the retraction. Likely several copies of myosin proteins act in a synchronous fashion to bring about the tentacle motion.

?The insights we gained into the properties of filopodia retraction and the possible molecular mechanism underlying them could find applications in nanotechnology,? says Alexander Rohrbach a former member of Stelzer?s group who is now a professor at the University of Freiburg. ?Future synthetic nano-machines must integrate themselves into a system and have to react flexibly to changes within the system. Precisely these properties we have now observed in filopodia retraction. The fascinating principles, which we are beginning to understand, will certainly influence the design of such machines?

Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.

Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....

Proteins must be folded correctly to fulfill their molecular functions in cells. Molecular assistants called chaperones help proteins exploit their inbuilt folding potential and reach the correct three-dimensional structure. Researchers at the Max Planck Institute of Biochemistry (MPIB) have demonstrated that actin, the most abundant protein in higher developed cells, does not have the inbuilt potential to fold and instead requires special assistance to fold into its active state. The chaperone TRiC uses a previously undescribed mechanism to perform actin folding. The study was recently published in the journal Cell.

Actin is the most abundant protein in highly developed cells and has diverse functions in processes like cell stabilization, cell division and muscle...

Scientists have discovered that the electrical resistance of a copper-oxide compound depends on the magnetic field in a very unusual way -- a finding that could help direct the search for materials that can perfectly conduct electricity at room temperatur

What happens when really powerful magnets--capable of producing magnetic fields nearly two million times stronger than Earth's--are applied to materials that...

The quality of materials often depends on the manufacturing process. In casting and welding, for example, the rate at which melts solidify and the resulting microstructure of the alloy is important. With metallic foams as well, it depends on exactly how the foaming process takes place. To understand these processes fully requires fast sensing capability. The fastest 3D tomographic images to date have now been achieved at the BESSY II X-ray source operated by the Helmholtz-Zentrum Berlin.

Dr. Francisco Garcia-Moreno and his team have designed a turntable that rotates ultra-stably about its axis at a constant rotational speed. This really depends...